What does "while you have (the specified card) on the field" mean, exactly?

This card is linked to a Digimon. If this card activates a link effect, is that effect considered a Digimon effect or an Option card effect?

Due to an effect, I can't use an Option card. Can I pay this card's link cost and link to one of my Digimon?

Can I also use this card's [Main] effect to link to a Digimon in the breeding area?

I used BT24-085 [Dan Yuki & Kanan Yuki]'s [End of Your Turn] effect to use this card, and I used its [Main] effect to link this card to my Digimon. If I then use the part of BT24-085 [Dan Yuki & Kanan Yuki]'s [End of Your Turn] effect after "then" to have the linked Digimon attack, can I activate this card's link effect?