1) Ch. 6, v. 12: "Vaani aral s'fosoyim" And I have clogged lips Rashi explains that in response to Moshe's attempting to excuse himself for being reluctant to be Hashem's spokesman to Paroh because of his speech impairment, Hashem advised him that Aharon would accompany him and be the actual spokesman. If so, why was Moshe needed at all? Why not have Aharon do the task all on his own?
2) Ch. 6, v. 26: "Hu Aharon uMoshe" They are Aharon and Moshe Rashi explains the reversal of order in the next verse. Their order is interchangeable because they are equal. This is difficult to comprehend because one of the 13 tenets of our faith is that Moshe is unique among all the prophets, not only in his generation and the previous ones, but for all further generations as well.
3) Ch. 7, v. 17: "V'nehefchu l'dom" And they will change into blood We are well acquainted with the order of the plagues, "dom, tzfardei'a, kinim," etc. However, we find a different order in T'hilim 105. How are we to resolve this?
4) Ch. 8, v. 20: "Tishocheis ho'oretz mipnei ho'orove" The earth WAS destroyed by the mixture of animals Literally, "tishocheis" means "it WILL be destroyed," as there is no "Vov hamha'peich" here. Nevertheless, Rashi says that it means past tense, although he gives no explanation for this. How can we explain this word in context to be in the future tense?
5) Ch. 9, v. 26: "Rak b'eretz Goshen asher shom bnei Yisroel lo hoyoh borod" Only in Goshen where the bnei Yisroel were present there was no hail If a ben Yisroel was outside Goshen would it hail upon him?