Send xray. It depends upon the technique of doing treatment. Do as suggested by your dental surgeon.

you can do two at a time if on the same side.  with in two sittings it should be completed.

There are few factors to be considered- 1. If all 4 teeth are located on same side of your jaw it is easier to do the RCT  , if not Dr may hv have to anaesthesize both side of ur mouth 2. Severity of infection : If the affected tooth is not having any underlying pus ,RCT can be done in single Sitting 3. duration  of the treatment - 1 RCT  ..single sitting may itself take up to half hour or more, so u can calculate  yourself. 4. Availability  of Dr. 5. U have to visit after few days for caps

This is determined according to the location of the teeth being treated,  facilities available and time at last. Adjacent/opposing teeth can be treated simultaneously. However, your doctor will give you final word on it.

rct can b done together or not depends a lot upon site of the tooth.same side but opposite arches can b treated simultaneously.Its always better to complete oneside first,b comfortable in eating n then go for the opposite side