It seems that this topic is along the lines of “if you ask 10 economists what they think of the economy you’ll get 10 different opinions”!
Certainly it’s wrong to say that “all 5 are not a sin”.
Suicide is usually treated these days as a symptom of something underlying rather than a deliberate wilful act. As such we would wish to treat the suicide victim mercifully and trust to God’s mercy that it isn’t necessarily ‘mortal’.
Taking the Lord’s name in vain is serious indeed, the utterances you have in mind will only be sinful depending on their context. If uttered for the purposes of cursing, then yes, gravely sinful and blasphemous. If uttered in surprise, then as said, not fully assented to. We are, of course, surrounded by idiomatic usages of sacred words, so the intent is what matters here.
It is permissible to miss a Holy Day of Obligation if one is completely unable to attend Mass on that day (for reasons of necessary work, sickness, necessary travel). However, we should be aware that there are such days on our calendar and do our best to mitigate the impediments to attending Mass if we can. That might not be possible for a doctor, for example, who is expected to conduct an operation on that day. It certainly IS possible for your average office worker who has the opportunity to use leave time or a personal day in order to be able to attend a Mass on an obligated weekday.
Cursing can definitely be rude and stands the chance of offending others. It should be noted that many curse words have their roots in religious language (bl–dy, for example, being a reference to the spear in Christ’s side, ‘gosh’ being an avoidance of using the name ‘God’, etc), so be aware of the context and the effects of saying such words. It is unlikely that saying the F word in private counts as sinful, although one should avoid forming the habit such that you come out with it in public and offend someone. At the point at which you carelessly hurt someone else’s feelings you’re probably committing a venial sin.
Abortion is simply a big no-no. It is never permissible. It is possible that a medical procedure carried out on a pregnant women for the necessity of saving her life has the accidental side-effect of causing a miscarriage or still-birth and (and, although this is my honest belief, I might need correction if I’m wrong on this) sin isn’t present, but the ending of the pregnancy should not ever be the primary object of that procedure.
As far as Orthodox Church attendance goes, I believe we hold that their Communion is valid, but that since we are not IN communion with them, therefore we should not expect to be able to receive Communion in an Orthodox church except and unless there is a very exceptional grave reason why it should be necessary - i.e. the imminent danger of death of the communicant concerned and that there is a lack of any Catholic clergy within reach. In general cases, I think that many Orthodox churchgoers would be scandalised if they were aware of Catholic persons receiving Communion at their church, since that person would not have been formally accepted into their community. While Catholics may be permitted as part of the rules of our Church in exceptionally grave circumstance to receive Orthodox Communion, I have no idea what the rules of the Orthodox Churches are in that respect. It’s possible that they might even prohibit it.
