Based on what another user posted in a different thread, the Netflix app on the older devices never supported captions, so there is no way to enable them,. Looking at the Wiki page that describes what each model supports, the 2050 only supports 1080p at p24 or p30. If the stream is 1080p/60, ir won't work. In that case, 720p is the highest resolution it supports.
The 2050 was first released in September 2010, so in electronic years it is ancient. I believe that the channel store will only show channels that will work on that device, so it you see it in the store it should work. However, I'll caution you that just because it will install and work doesn't mean it's actually usable. For example, the YouTube channel will still install and work on my 2 XS (just under a year newer than your 2050), but for all practical purposes it's unusable. It responds to remote command so slowing it's frustrating. There are likely many more like that on a player that old. Honestly if you could scrape up $25 for a new Express (on sale at the Roku web site) you'd be much better off.