2. Then, on "Э-Е" thing:

Yes, they normally make different sounds, However, "Э" is very rare in native Russian words. It only exists in indicative pronouns (это, этот, эта, эти - this, these, and all their declension forms), in exclamations (эй! эх! э-ге-гей!) and in derivative words like "поэтому" (therefore, because of that) - formed as "по" + "этому" (literally: on-this).

But there are a lot of foreign language borrowings which have Э: этаж, экскурсия, эскалатор, поэт, поэзия, силуэт, экономика, эпоха, эра - many of them are cognates with Western languages since they mostly come from Latin or Greek (sometimes - from English).

In the beginning of a word, or after a vowel, the difference between Э and Е is basically the same as between English "E" and "YE". English words like "end, else, egg, elbow" would be transcribed in Russian as "энд, элс, эгг, элбоу". And the words as "yet, yes, yellow, yesterday" would be transcribed in Russian as "ет, ес, еллоу, естердей". So, we pronounce (approximately!) "это" as "ET-tuh", "этаж" as "et-TAHZH", but "ель" as "YEL' ", "если" as "YES-lee"; "поэт" as "puh-ET" but "поел" as "puh-YEL".

But when after a consonant, Russian Е does not produce any "Y" sound, it only palatalizes ("softens") the preceding consonant: "тело" sounds like "T'EL-luh" where the initial T is palatalized. Э after a consonant is only written in a few loan words to show the consonant is not palatalized (мэр, пэр, сэр).

3. The soft sign (ь) changes the sound of a consonant making it palatalized.
For Russians, the following words sound completely different: вес (weight) - весь (all, whole), полка (a shelf) - полька (a woman from Poland), кров (literally "roof" - a dwelling) - кровь (blood), цел (undamaged) - цель (aim, goal), быт (daily life) - быть (to be), горка (a little hill) - горько (bitter, sad), всем (to everybody) - в семь (at seven) etc. etc. So, we just use this letter according to the pronunciation