I attend daily Mass in either Portuguese or Polish.

Sometimes, I can pick up that the Collects and Responsorial Psalms are different from what I'm following in my iBreviary app. Are there times where there are multiple options? Because the app I have doesn't list them.

Also, this may be relatively minor, but it kinda ticks me off... how many Alleluias are there suppose to be?

One Mass I go to has the person saying/singing Alleluia three times, and then the congregation responds three times. Other Masses, it's only twice, where the congregation responds twice.

There are often options at daily Mass. Some saints' feasts are optional, and sometimes there are multiple saints available on a day.