What do you think? Righteousness?
You posted: If repentance is fully preached from Scripture (Acts 2:38) then repentance is the other side of believing. "Except ye repent, ye shall all likewise perish" is what Christ said.
Depending on context, repentance can have a variety of meanings. You cited Acts & Luke. In each verse the meaning is different.
Additionally, repentance was being tied to salvation as being necessary & it is. Yet, not applicable to salvation in either vs cited.
In Peter the context is: Jesus is Messiah & you had him KILLED. You need to repent from your actions. Believe He's your long promised Messiah. In short repent/change your mind from unbelief to belief!
In Luke, Jews are gossiping about some Galilaeans (thought to be really far outside of covenant seals) they had committed a heinous act. By mixing blood with sacrifices. Jesus tells these self-righteous tattle tails. Truth, your own godless unfruitful actions make you jus as guilty/repent & return, to walking with & bearing fruit for God.
The perceived thought/notion as to why the tower fell down on the ones it did. Was because the Galilaeans as a whole were known to be ungodly. Jesus says you think because you're actions aren't as ungodly as theirs, your ok. Well, you're not ok, you have tuned your back on God & are just as guilty/unfruitful as they are, repent/return to the the Lord your God.. The unfruitful fig parable is levied against the whole nation.
There was some covenant mixing in the OP as well. The kingdom message Jesus preached is void of the death & resurrection (he's still alive) and the NT indwelling Holy Spirit. Isn't poured out until 50 days after His resurrection. Both are critical center pieces to the Gospel of grace message Paul preached to the NT Body of Christ.
1 Gospel/Good news message. What's the good news? God via his merciful grace. will provide sinners a way/path to a full sin pardon.
God, 1st revealed his plan of redemption/sin forgiveness/reconciliation to Adam & Eve. When he covered them with/in sacrificed animal skins (Gen 3:21).
Later on Mt Moriah, God, reveals his plan of redemption/sin forgiveness/reconciliation to Abraham (Gen 22:14). The message in both dispensations is God's path to redemption is coming, trust Him!
Next the kingdom gospel, it's message of redemption is: The redeemer is here acknowledge Him!
Under the gospel of the grace of God message: The good news is: Jesus death &n resurrection HAVE provided the pathway to salvation/forgiveness, Put your Faith in His finished sin redemptive work!
Lastly, in every case. Faith in God/Christ is the conduit to accessing salvation.
One gospel (3 dispensations), God is the redeemer & sin redemption is accessed by FAITH placed in His plan.