Seeking details on "teliyah", dangling missing words in a Sefer Torah

Question

Can one add in missing words above the line in a Torah scroll? discusses an example of adding in a missing word in a Sefer Torah. The answer gave a reference Shulchan Aruch YD 276:1, but it is very brief, as is the gemara it comes from, Menachos 30b. I was hoping others can provide more information, and sources:
a) How do we know to be תולה above the words (as in the picture) rather than below? Is below allowed (presumably staying closer to the line above than the line below)?
b) I think someone suggested that we are תולה just above the next word?
c) Related to the previous question - if one is being תולה more than one word, or even an entire verse or more, how in the world can you tell where it should fit in the surrounding lines?
In my youth when I used to add something in English to a line, you'd write above or below and then mark the spot in the original phrase with a V or Λ above or below where the new words should fit it. I'm certain you can't do that in a Sefer Torah.
d) I found a couple of images online, but not much discussion. Are there a lot of examples of this to see somewhere?

Answer 1

a) It was probably considered obvious, but you occasionally (eg. YD 273:6, 276:12) find incidental references to "למעלה above" which clarify that the intention is to hang the missing text above the line. I haven't seen anyone discuss what happens if you put it only below the line but I'd guess it's only kosher if it is written in such a way that it is clear where the text is supposed to be inserted (perhaps analogous to Tashbetz 1:176).

b) See Melekhet Shamayim (25:6):

ושתולה התיבה שחסרה בין השיטין מתחיל כתיבתה מכוון למעלה על התיבה ששייכה אחר התיבה החסרה, ולא יתחיל לכתוב התיבה החסרה מרוחקת לצד ימין יותר מן התיבה שלמטה ממנה וגם לא ירחיקנה לצד שמאל יותר מהתיבה שלמטה, אלא במקום שהתחיל האות הראשונה של תיבה שלמטה שם יתחיל האות הראשונה של התיבה שלמעלה, ועל כל פנים אם מגיע תחילת התיבה שבין השיטין מכוון עד סוף התיבה שלפניה שתחתיה פסול.‏
When hanging a missing word between the lines, start its writing aligned above the word that belongs after the missing word, and don't start to write the missing word far to the right of the word below it, and also don't distance it far to the left of the word below it, rather in the place that begins the first letter of the word below, there should start the first letter of the word above, and at the very least if the beginning of the word above reaches to the end of the word before it it is invalid.

c) You can't use marks to indicate where the word should go (ibid.). Some allow a very long passage of text to be inserted by continuing onto the next couple interline spaces, arguing it is obvious because of the cramped writing that it all goes together to be inserted at the starting place, while others do not allow that (see Aruch Hashulchan YD 276:12-14).

d) It happened often enough in old Torah scrolls, but nowadays it almost never happens (cf. Benei Yonah 25b). The market is such that for a scribe who erred it's usually worth it to rewrite whole columns or pay for fancy expert erasures to ensure the product isn't "ugly". But it's hard to say it's no longer kosher if you did it, and indeed I've seen it happen on rare occasions.