Masjid Aisha and umrah question

I am going for umrah, my first question if im going to perform a second umrah, can I do the ghusl wear the ihram at the Makkah hotel before going to masjid Aisha and then when arrive there I do the intention? My second question is the ghusl before umrah is intention ghusl for umrah or just intention for ghusl as we do every day? Third question Niyat itikaf I know I have to read this at masjid al haram to be able to eat drink etc, but don’t know the exact reason, do I have to read the Niyat at other mosques , do I have to read this at masjid nabawi as well or only in Makkah ?