Across all instances

Yes its so you can use any mastodon account

Mammoth has a For You tab and I found it quite useful

Looks like someone created a pull request (a code submit) for iOS client last month then conversation stopped

Do you have Elite? Their free version seems enough for me but I saw no Ads on elite which means it likely has ads in the free version

I wonder if it has many/in the way ads before trying out

This is still unclear for me to understand how sync works, because if it does not suit me, mo way I would be using it.

For example I mostly type on mobile, then when I open my laptop, the app will try to sync between my phone and my laptop, with their server helping establishing the connection? I don’t see how its gonna work well since both has to be online and have good Internet at the same time

While looking good on desktop (based on screenshots), it is definitely not designed for mobile. See below