Here, Ānanda, when a bhikkhu sees a form with the eye, there arises in him what is agreeable, there arises what is disagreeable, there arises what is both agreeable and disagreeable. He understands thus: ‘There has arisen in me what is agreeable, there has arisen what is disagreeable, there has arisen what is both agreeable and disagreeable.
Idhānanda, bhikkhuno cakkhunā rūpaṃ disvā
uppajjati manāpaṃ, uppajjati amanāpaṃ, uppajjatimanāpāmanāpaṃ. So evaṃ pajānāti: ‘uppannaṃ kho me idaṃ manāpaṃ, uppannaṃ amanāpaṃ, uppannaṃ manāpāmanāpaṃ.
The Sanskrit रननाप manāpa [mana_āpa] means lit. “reach the manas”.
So what is agreeable (manāpa,) or disagreable (amanāpaṃ) , or both ( manāpāmanāpa,) seems to be related to “reaching the mano”.
As for MN 39 (that you quoted above, these are the differences between mano (the internal base/field of experience) & citta.
Bodily, verbal, and mental (mano) behavior must be pure.
When we know a thought with our mind (mano), we won’t get caught up in the features and details.
manasā dhammaṃ viññāya na nimittaggāhī nānubyañjanaggāhī.
If the faculty of mind was left unrestrained, bad unskillful qualities of desire and aversion would become overwhelming. For this reason, we will practice restraint, we will protect the faculty of mind, and we will achieve its restraint.’
Yatvādhikaraṇamenaṃ manindriyaṃ asaṃvutaṃ viharantaṃ abhijjhādomanassā pāpakā akusalā dhammā anvāssaveyyuṃ, tassa saṃvarāya paṭipajjissāma, rakkhissāma manindriyaṃ, manindriye saṃvaraṃ āpajjissāmā’ti evañhi vo, bhikkhave, sikkhitabbaṃ.
We see that the faculty of mind (mano) must be restrained, not to allow unskillful qualities of desire and aversion to become overwhelming.
This is the development of the mano towards the external field of sensory experience bahirani ayatanani
This is vivekka.
When practicing walking and sitting meditation by day, we will purifying our mind (citta) from obstacles.
Divasaṃ caṅkamena nisajjāya āvaraṇīyehi dhammehi cittaṃ parisodhessāma.
Idem at night.
Giving up desire for the world, they meditate with a citta rid of desire, cleansing the mind (citta) of desire.
So abhijjhaṃ loke pahāya vigatābhijjhena cetasā viharati, abhijjhāya cittaṃ parisodheti.
Idem with the other hindrances (ill will, dulness & drowsiness, overdoing and underdoing [the latter might bring remorse], doubt).
When their mind (citta) has become immersed in samādhi like this—purified, bright, spotless, rid of taints, pliable, workable, steady, and imperturbable—they extend it toward recollection of past lives.
So evaṃ samāhite citte parisuddhe pariyodāte anaṅgaṇe vigatūpakkilese mudubhūte kammaniye ṭhite āneñjappatte pubbenivāsānussatiñāṇāya cittaṃ abhininnāmeti.
Idem for the knowledge of the death and rebirth of sentient beings - and the knowledge of the ending of defilements.
Knowing and seeing like this, their mind is freed from the defilements of sensuality, desire to be reborn, and ignorance.
Tassa evaṃ jānato evaṃ passato kāmāsavāpi cittaṃ vimuccati, bhavāsavāpi cittaṃ vimuccati, avijjāsavāpi cittaṃ vimuccati.
Note that piti and sukha occur in jhana - while pamojja and somanassa occur when one is freed of the hindrances.
“They gain even what is hard to gain,
“Who delight in calming the citta ,
Whose mano, day and night,
Take delight in development.”
In one who has joy, delight arises. In one who has delight of mind ( mano ), the body becomes serene. When the body is serene, one feels pleasure. Feeling pleasure, the mind ( citta) becomes centered (concentrated). When the mind is centered, phenomena become manifest. When phenomena are manifest, he is reckoned as one who dwells heedfully.
Pamuditassa pīti jāyati. Pīti manassa kāyo passambhati. Passaddhakāyo sukhaṃ vediyati. Sukhino citta ṃ samādhiyati. Samāhite citte dhammā pātubhavanti. Dhammānaṃ pātubhāvā appamādavihārītveva saṅkhyaṃ gacchati. Evaṃ kho, nandiya, ariyasāvako appamādavihārī hotī”ti.