1) In 39:10 concerning someone who puts on Tefillin only LePrakim they need to have their Tefillin checked twice in a Shmita. The Rema adds if no one is not able to check them one should still don them. The Mishna Berura questions whether one could recite a Blessing on them and concludes with a Tzarich Iyun. Lemasah what is the conduct in this case, this is a very frequent problem that someone got a pair of Tefillin from a relative (therefore it would be considered manichim leprakim) or a pair of Tefillin for Mivtzaim etc.. if they were not checked within 3 and a half years should a bracha be made over them?
2) On a Shaylos Tinok, when the ois hamasupak is next to another identical letter either in the same word etc..
If by covering or revealing the identical letter next to it could help the tinok (mitchakem) to either call it, possibly to be lehachmir or lehakal. Should such letters be covered or not? I have not found this exact question discussed openly in Sefarim. Although I think in general it does not make a difference based on the 2 following sources, there are though some exceptions.
a) The well known opinion of the Shulchan Aruch HaRav (32:21) that there is no need to cover the letters adjacent to the letter in qestion.
Does this also refer to such a case?
b) The Mikdash Maat 32:57 writes if a tinok called the letter incorrectly and afterwards the person showed the tinok the rest of the letters so he fixes himself and recalls the letter correctly we rely on the tinoks later correct calling.
From here we see that we do not care (to allow the tinok to Mitchakem even lehakal) so long as he is not a Chacham (and not a tipush). However there is a certain limit to how much we can machkim the tinuk, as I posted earlier with a Beis which resembled a Mem Sofit, from the word Yirbu, my Rav told me to cover the vuv at the end of the word to see if the tinok will call the beis a mem sofit (and he did).
It is also well known that when there is a doubt on the length of the ן of the word פן we cover the פ because it goes down low, the tinok might call it a ז in comparison to the low פ.
These are 2 example cases where we will cover letters to be either lehakal or lehachmir. These examples were mentioned in context of final letters where it would be a "given" if we do not consider that the final letter plays a factor in the conclusion the tinok will make. (I later found that the Gidule Hekdesh (Klalim 14:6) writes clearly on letters which could appear like a final letter that the rest of the word must be covered, so the tinok will not be influenced by external reasons, and decide only on the basis of the tzura he sees).
Interesting to point out, I found in Shavet Halevy vol. 5 6:2 where he quotes a rule that we never posul a letter based on judging it next to the other letter if it is kosher mitzad otzmo. However see also ibid 6:152 where sometimes a doubtful letter (because of length) can be effected (for example a longer yud against a shorter vuv) when we put them together, the 2 letters look similar, here we show the tinok and he is machria. The reason to this is that one letter has to be wrong and that is why it is shailos tinok. In general the poskim stress that we are not interested in posuling lechinam, therefore we will sometimes machkim the tinok (get them use to some of the letters etc..). It is also understood that we will not "spoon feed the answer" to the tinok.
I find this topic very relevant today, I myself have come to many difficult situations in these questions. Most recently in a mezuza the word "levavacha" there is בב and the first one had a descending little shpitz that gives it a possible appearance of a Gimel. If I show the questionable ב alone it was called correctly as a ב. If I however show both of the ב it was called a gimel, since the tinok compared it to the second distinct ב. What do you think the halacha is over here. It seems to me that we need to show both ב together and therefore the mezuza would be posul, since the tinok called it a gimmel. (Similar to the cases mentioned in Mikdash Maat and the Shavet Halevy vol. 6:152).
I assume there are other special exceptions to this rule and would appreciate if anyone has some examples or rules at hand.