Q1:Does the magnetic car mount can used with iphone 6plus? I think my phone is very heavy.
Dear buyer,it is strong enough to hold your phone as it is stable and rotatable to fit with the different angle you need.
Q2:will it work if your iphone is in an otter box?
It needs a hard surface for the adhesive disk to stick on the back of the phone. I've had an ottobox, great box but if it's a rubber membrane type it won't work as it needs stick or stay on a hard shell and as it will attached to the ball via magnetic. I have a iPhone 6s Plus with a life proof box, works great except for the life proof issues with quality by sound thru t speaker. Hope this helps.