How to install redis for free hosting?

You should read the post Greenreader9 linked.

Quoted from the post:

If you really want to use Redis in your site, you can still get a Redis server elsewhere and use the pure PHP predis library to interact with it. Sure, the native PHP extensions are faster, but performance is out of the window anyways if you use a Redis server in a different datacenter.

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According to the post, yes.