Unfortunately you can't manage notifications per account.
But you can use a separate MetaTrader terminal installations to use different settings in each.
Not clear for me.
Please address to a ServiceDesk with log files attached
You cannot install custom indicators to the mobile/android versions of MT4 & MT5.
You can only use the default ones, that come with the app.
No, it is not planned. But the Signals service will be launched. You will be able to subscribe to any participant account.