Question: where to watch old episodes of doctor who?
Answer: If you don't care what order you watch in, Pluto TV (free app for Fire TV, Roku, Apple TV most Smart TVs and webpage) has a free live channel that airs classic Doctor Who 24/7. If you want legal VOD there's Britbox (app for Fire TV, Roku, Apple TV and web) which has it for around $6 a month.