yes 

if the normal savings account you meant is basic savings account, yes they do have interest albeit the interest is very low.

yes, to enjoy higher interest you can deposit your money into m2u savers account.

Got. Your card is linked to your basic account. You cannot make purchase from your m2savers. You will need to transfer to your basic account first. Your basic account will most likely be charged rm8/year. There's a way around it. Make a normal basic account with 4x/month withdrawal. That's free. So when you want to withdraw cash from atm, just pick others instead of your basic account. M2savers allow unlimited withdrawal.

You can do like me. Transfer any unused money into Ambank Truesavers (earns 2.8% p.a instead of M2savers which give only 2.25% p.a no minimum amount required - m2savers required min rm2k in your account, no need to topup every Month, free IBG) Bad thing is ambank Truesavers have no IBFT and allow only 3x withdrawal (atm+online transfer) per month.

yes that's true. both accounts will be linked under the same debit card.

however to purchase stuffs online, do take note this FAQ on Unsecure Online Transaction