working days in Ethiopia???

Banks are closed on Sunday for sure. Finding accomodation allover Ethiopia should be no problem. Without having done the trek in Lalibela I would say, Simien and Tesfa trek are not comparable at all. I drove through parts of the area of Lalibela and also screened a lot of photos and by sight it's a completely different landscape. Simien mountains are breathtaking, Lalibela surroundings are nice, nothing more. It's also a different approach to trekking which they offer in the Tesfa trek, maybe in this regard (embedding tourists) tesfa trek is better than Simien.

No, the treks are not the same at all. The TESFA trek is on a plateau, average altitude 3000m. Simiens are a mountain range, will have far more striking scenery, although the TESFA trek is beautiful in its own right. You will likely meet far more people on the TESFA trek, which is what appealed to me, as well as know that you are supporting the community.

For trekking, TESFA is relatively luxurious. Well-constructed camps, excellent food, English-speaking guide + local community guides, porters w/ donkeys--which is what led them to raise the price to 450 birr per day compared to the 300 birr/day I paid just a year ago. This price does not included bottled water.

My understanding is that a Simiens trek should cost 300 birr/day max, all-inclusive, but I'm sure someone has posted recent info on that.

Banks in Addis on Sundays.

Best plave to change money in Addis are the 2 banks on ground floor of Hilton and they are open on Sundays.

Re booking. Really no need to book in advance
possible exceptions,.

Gondar IF you want to Goha and only the Goha

Murell Lodge in Omo..