Yes, all mortal sins should be confessed as soon as possible and one should abstain from receiving Communion until one had been absolved - or else one is guilty of committing sacrilege - another Mortal Sin.
Mortal sins destroy our relationship with God and depending on the gravity could lead to damnation if one dies without confession.
See the Catechism of the Catholic Church for more information on sin 1855-1874.
Though it is recommended to confess all sins, the only mandatory ones to confess are mortal sins. Sins that have been committed with full intention of committing it, full knowledge of how evil it is, and that are grave sins (All three conditions must be met for a sin to be mortal).
Mortal sin must be confessed in penance. The priest will tell you whether a sin is mortal. Mortal sins are when you break an important law of God or the Church and do so on your own free will and with sufficient knowledge of what you're doing. If you are unsure whether you should confess something, it is best just to confess it anyway. Confessing lesser sins is optional but recommended.
You need to confess your sins to a priest in the sacrament of reconciliation
You can receive the sacrament of Penance if you have any sin including not only mortal sins but venial sins as well. If you have sin, it is recommended but not necessary to receive the sacrament (Except for mortal sins where you must confess it)
Venial sins can be, but mortal sins can only be forgiven through the sacrament of penance. Although it is recommended to confess venial sins in the sacrament of penance as well.
The Pentitential Rite at the beginning of Mass is when we confess our sins and are absolved by the priest's blessing of venial (less serious) sins. Mortal (serious) sins must still be confessed in the sacrament of Penance (Confession).
Catholics must confess their sins to a priest as this is the only normal way in which Our Blessed Savior left for people to have their sins forgiven. Less serious sins (venial sins) may be forgiven with a good Act of Contrition and Holy Communion. Serious sins (mortal sins) may only be forgiven at Confession. Besides the Church requires that all adult Catholics must go to confession at least once a year, even if they have not committed any mortal sins. Any good Catholic who is sincerely trying to fall Christ and become perfect (Matthew 5:48) should be going to regular confession, weekly or at the least, every other week.
Yes, but technically, we confess our sins to God through the priest.
Yes, you do have to confess your sins & get baptized in the Holy Spirit to go to heaven.
There is no precise list of mortal sins in the Catholic Church.
Mortal sins are more serious than venial sins, and they have more serious consequences: With mortal sin, the life of grace is lost and the sinner is in danger of hell. With venial sin, the life of grace is weakened but not lost. Even so, venial sins should not be taken lightly, since habitual venial sins can harden one to commit mortal sin.
James 5:16 " Confess therefore your sins one to another: and pray one for another, that you may be saved. For the continual prayer of a just man availeth much." Matthew 9 shows that Jesus gave men power to forgive sins. Confession forgives us our sins and gives us the grace to stop sinning. Through baptism, we enter into a friendship with God; through confession, we mend our relationship with Christ after sin. In confession, we don't just confess to a priest but to Christ who works through the priest.