Trade all your profits in Bitcoin
If you trade back into Ethereum or BNB eventually trade back to Bitcoin
No.
Put 5k in profit into BTC for 5% gains/going sideways or put that 5k into an alt that can potentially 2x the next day. Even a 20-30% gain will probably outperform BTC. When BTC dominance is down and alts season is in full bloom you better maximize your gains.
You can make enough off alts to buy a whole BTC or a decent chunk.