Am I correct that one can take the Elizabeth Line from Reading Station to London Heathrow ?
Yes but you have to change platforms at Hayes & Harlington. You can plan your route on TFL https://tfl.gov.uk/plan-a-journey/ or using an app like CityMapper.
Here is the full Elizabeth Line route map and timetable:
https://tfl.gov.uk/cdn/static/cms/documents/elizabeth-line-may-2025.pdf
Yes, but I'd suggest the bus instead. https://www.railair.com
I just took the bus from Heathrow to Reading. Takes less than an hour, and the bus driver puts your suitcase under the bus. Much easier to nap than on the Tube :-)
Hair splitting comment.
Technically Elisabeth Line is not on the tube. As a passenger you will not notice - except that on Paddington you are not entering in the Tube area, but on a separate platform; and the trains are much newer and nicer :-)