If you connect the 2nd extender to the main network that would be ok. If 2nd extender is connected to the 1st extender, its possible but expect a slow connection.
That I am not sure of as it depends on the environment. If the connection from the 1st extender is cut into half then probably can get 1/4 or less with your subscribe speed.
WiFI CSMA/CA protocols prevent simultaneous transmission from devices sharing the same channels (or overlapping channels), devices have to ‘listen’ and wait for clear air-time before transmitting. So any device with a single radio will by default reduce throughput by half, do this twice and throughput would be less than a quarter. Add losses due to range and obstacles and double repeating can be very problematic and disappointing.
