In my variety of Nepalese (in Kathmandu), the pronouns उनी / यिनी / तिनी is seldom used. However, I know that it's very present in the mountains. However, if you were to use these pronouns, you would be perfectly understood in Ktm and it would actually sound rather cultuvated although a little rural. If you were to use it you can indeed think of this as a formal way of speech and it's pretty neutral (I am thinking that's what you mean by middle). ऊ is a pronoun and is used for people only. You would only use it for people younger than you are in which case it is (informal) and neutral . However, यो त्यो are mostly used like defenite articles (eg. त्यो केटो छुच्चो छ|) even though in some cases you could use them as pronouns (eg. त्यो छुच्चो छ|). These are informal and it shows that you have less of a respect for the person (so low form based on your scale). You are right about यहाँ / वहाँ / उहाँ but a quick note though, I think most people use वहाँ and उहाँ interchangebly and I personally have never used यहाँ. So In short: उनी / यिनी / तिनी formal and cultivated form of speech (mostly obsolete in Ktm) ऊ informal and neutral when referring to people younger than yourself यो त्यो informal and shows a lack of respect (so low) वहाँ / उहाँ formal and respectful I hope this helps!

In Nepali, u, yo, tyo or uni, yini, tini are used 1. for somebody who is younger than you (let's say or 5 or more years) 2. among friends of same age group. The formal or informal is used in an office depending upon the closeness between the person talking and office setting (work culture). u, yo S/He This >> for somebody younger and friends. uni, yini, tini >> for somebody younger and friends but you give them some respect because either you are not that close with them or if they posses some special talent/skills etc. Let me know if I wasn't clear enough. Good Luck.