ios - iOS: UIScrollView leaving space on bottom, How can I have space on top

Question

I have scrollView in which subview are getting added from bottom, like adding bricks in wall (in my case only one brick), then next brick on top of that, like that so on. As with default UIScrollView ContentSize, Scrolling will happen on top. How can I make scrolling to bottom. If I scroll down I should be able to see other bricks which are added one above the other.

As you can see in below screen shots, start button should go down instead of of up.

Any kind of help be very appreciated.

Thanks

Sample Code:

CGFloat initialYPoint = 30;
for (OUSTLevel* currentLevel in self.course.sortedLevelsList) {

    NSArray* nibList = [[UINib nibWithNibName:@"OUSTLearningMapPlayLevelCell" bundle:nil] instantiateWithOwner:self options:nil];
    OUSTLearningMapPlayLevelCell* playLevelCell = nil;

    for (UIView* childView in nibList) {
        if ([childView isKindOfClass:[OUSTLearningMapPlayLevelCell class]]) {
            playLevelCell = (OUSTLearningMapPlayLevelCell*)childView;
            break;
        }
    }

    CGFloat cellHeight = CGRectGetHeight(playLevelCell.frame);
    CGFloat yPoint = CGRectGetHeight(self.scrollview.frame) - (cellHeight + initialYPoint);
    CGRect cellFrame = CGRectMake(0, yPoint, viewWidth, cellHeight);

    [playLevelCell setFrame:cellFrame];      
    [self.scrollview addSubview:playLevelCell];

    initialYPoint += cellHeight;

    if (!landingNodeLevelData.locked) {
        [playLevelCell.unlockedView setHidden:NO];
        [playLevelCell.lockedView setHidden:YES];

        // Frame calculation for placing pin
        CGFloat centerPoint = playLevelCell.unlockedView.frame.size.width / 4;
        pinXPoint = centerPoint + 5;
        pinYPoint = yPoint - 30;
    }
}

CGRect pinFrame = CGRectMake(pinXPoint, pinYPoint, 80, 80);

[self.pinImageView setFrame:pinFrame];
[self.scrollview addSubview:self.pinImageView];
[self.view bringSubviewToFront:self.pinImageView];
self.scrollview.contentSize = CGSizeMake(self.view.frame.size.width, initialYPoint);
self.scrollview.contentInset = UIEdgeInsetsMake(30.0, 0.0, 30.0, 0.0);
CGPoint bottomOffset = CGPointMake(0, self.scrollview.contentSize.height - self.scrollview.bounds.size.height+ 30);

Edit: I am not using constraint layout, I am calculating & setting frame.