Question: Will there be a connection problem if the same MT4 account is logged in at the same time from multiple devices?
No, MT4 trading platform allows multiple login simultaneously to the same account.
You can log into your account from the MT4 desktop terminal on your PC and sign in using your mobile phone while you are away.
If you prefer the third person to be able to see the account activity but not trade, you may provide him/her with “Investor Password”.