When you are getting started making actual trades, in general you should focus on making LIMIT ORDERS which will get FILLED by other traders. Not only will you pay lower fees this way, but you will also be making more composed trading setups because you aren't impatiently just market-buying or market-selling into the spread. So a general principle you should follow is to AVOID MARKET ORDERS WHEN YOU CAN! You will pay higher "taker" fees and you will be at the mercy of the spread which is a hidden fee.
Interest Rate Swaps. Interest rate swaps, in their most basic form, involve the exchange by a Fund with another party of their respective commitments to pay or receive interest. For example, a Fund might exchange its right to receive certain floating rate payments in exchange for another party’s right to receive fixed rate payments. Interest rate swaps can take a variety of other forms, such as agreements to pay the net differences between two different interest indexes or rates, even if the parties do not own the underlying instruments. Despite their differences in form, the function of interest rate swaps is generally the same: to increase or decrease a Fund’s exposure to long- or short-term interest rates. For example, a Fund may enter into a swap transaction to preserve a return or spread on a particular investment or a portion of its portfolio or to protect against any increase in the price of securities the Fund anticipates purchasing at a later date.

Fixed margin will isolate your margin to the individual position you have made in an instrument. So if you have 1 bitcoin in your account and you put 0.2btc margin for a Weeklies Futures long position, and it gets margin-called, you still have the 0.8btc left. However, if you're on cross-margin, also known as portfolio value margin, then your whole balance on the site is going to be used to back all your positions, and if you get margincalled, it's because you have run out of money on your whole account.

The Fund will periodically adjust its holdings in order to maintain inverse exposure to bitcoin futures contracts. As the price of bitcoin futures contracts declines, net assets of the Fund will generally increase resulting in inverse exposure that is less than the value of the Fund’s assets. Conversely, when the price of bitcoin futures contracts increases, net assets of the Fund will generally decrease resulting in inverse exposure that is more than the value of the Fund’s assets, and the Fund’s inverse exposure will be periodically adjusted to restore approximately equivalent inverse exposure.
With the increased use of technologies such as the Internet and the dependence on computer systems to perform necessary business functions, the Funds and the digital assets that underline the bitcoin futures contracts in which the Funds invest are susceptible to operational and information security risk. The digital nature of bitcoins and the irreversible nature of bitcoin transactions makes bitcoin an attractive target for theft, hacking and other cyber-attacks. In general, cyber incidents can result from deliberate attacks or unintentional events. Cyber-attacks include, but are not limited to gaining unauthorized access to digital systems for purposes of misappropriating assets such as bitcoin or other cryptocurrencies or gaining access to sensitive information, corrupting data, or causing operational disruption. Cyber-attacks may also be carried out in a manner that does not require gaining unauthorized access, such as causing denial-of-service attacks on websites. Such events have historically correlated with a drop in the price of bitcoin, which may adversely affect your investment in a Fund. Cyber security failures or breaches of a Fund’s third party service provider (including, but not limited to, index providers, the administrator and transfer agent) or the issuers of the bitcoin futures contracts in which the Funds invest, have the ability to cause disruptions and impact business operations, potentially resulting in financial losses, the inability of a Fund’s shareholders to transact business, violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, reimbursement or other compensation costs, and/or additional compliance costs. In addition, substantial costs may be incurred in order to prevent any cyber incidents in the future. The Funds their service providers, counterparties and other market participants on which the Funds rely could be negatively impacted as a result. While the Funds have established business continuity plans and systems to prevent such cyber-attacks, there are inherent limitations in such plans and systems including the possibility that certain risks have not been identified.

There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.