I can answer some questions. not all. i'll leave those to the mods or more experienced players.

2) the disappearance of the chakra training system. your elemental attack % should still be there btw. those stats wouldn't have disappeared.

4) Ninjas are also given for free here :) If you check the event shizuka/guren/shira/chiriku is given out in, you'll notice they need a token for every time they clap. It's the same principle behind redeeming ninjas for free here.

Also, the clothing system is different in CN. You get the outfit, but the clothing has to be levelled up. You start of with outfits that cost like 100 coupons and base stats of +5 nin/atk/etc. then you level them up using cloth like we do with our regular battle armour (lvl 2 is +10, lvl 3 is +15 or something). It's expensive. We pay for the clothes because it gives us the costume and the stats together.