How does Google TTS decide which voice to use? If a book is written in two or more languages, can TTS choose the language-voice pair (perhaps based on the information stored in a dictionary app or e-book)?

I read https://android.stackexchange.com/questions/66285 , and it says the command "pound sign" will produce a # for UK English which it does. How do I get a £ instead? My system language is English UK.

I think it would be nice if in the text-to-speech settings you could specify a cascading set of languages, with dictionaries, associated with each language, intrinsic in the language selection. When, a word is encountered, TTS would look up the word in the dictionary for the selected language, if it is not found, it looks it up in the dictionary for the second language, and so on. When a word is found in a dictionary, it is played, using the language intonation for the language associated with that dictionary. If the word is not found in any dictionary, the first language specified is used to pronounce the word, by default. This multi-language algorithm could be a bit more processor expensive, but several multilingual users who write their notes and text in their apps in more than one language at a time (even using the Feynman method, ie., write as text comes natural to you, rather than abiding by the rules of a specific language), for instance in their Google keep notes, might like this feature (and use it). Can this be implemented in Android? When will this be implemented? How can I enable it? Thanks.

Today, I got the update of Google Text-to-Speech on my HTC One X. I was able to configure it and even listen to an example. But how do I use it? The Play Store description states that it can be used with Google Play Books, Google Translate, and many other applications in Play Store. But what if I have a page on my Firefox or Pocket app which I want to read it out? How do I use Google Text-to-Speech with that? Also, this app does **not** show up in my app drawer. Any reason why?

I'm using Xiaomi Redmi Note 12 Pro (MIUI Global 14.0.6). I'm not able to set up the Catalan language in the Google TTS engine. Basically, it does not accept any language which is not linked to a country (like Croatian or Serbian for example). My phone system language is set to Catalan. Any other language linked to a country works. By languages not linked to a country, I mean those appearing on the list of languages which do not have the country next to the language e.g. English (United Kingdom). For Catalan, it appears as is in the list with no country next to the name. I guess if it would be listed as Catalan (Spain), it would work. Any support would be highly appreciated. I can't use another TTS engine as I'm using a Samsung 5 Pro smartwatch and the Samsung Galaxy watch manager app only supports 2 TTS engines: native Samsung TTS and Google. Unfortunately, Catalan is not supported by Samsung TTS (at least I was not able to find it). Thanks!