1.) dunno how many lessons a week but nat teacher will attend one lesson per week.
2.) they have a nat teacher, she is very nice
3.) yes, they have mandarin nat teacher, the same one lesson per week.
4.) should be no problem, as during the terms of K3, they have the 適應 class for the kids, dont worry.
as I remembered, why I chose WTT but not the taipo market, was the teachers of taipo market seems not so nice during the interview. but the same comments as you on WTT teachers, they all are very nice and very experienced.
I think WTT level is above the standard when I discussed with my friends about their kids' kindergartens. so it is no problem for the kids to match the P1.