2. Staking isn't giving huge returns but staking bitcoin or Tether with APY over 8% is somewhat profitable.
If you mean wBTC, I don't think the risk that defi possess is worth the amount of 8% APY, not to mention that it is also far from the true Bitcoin, holding bitcoin on its own network would give a better and safer return.
To do Yield farming, need I any special application? Can I use the Trust Wallet for Yield farming?
It depends on which platforms you would do the farms. Trust Wallet has DApps browser that shows on which platform they are able to connect, so if your choice of the platform listed there, I believe you can practically use Trust Wallet to do the job. But if not listed there, I would try to directly open the site and see if there is an option to connect using the wallet.